One thing about different breeds is that they all show that they are at or above threshold differently. I think that is one reason why people assume labs are so "high energy." Because when they are above threshold they are bounding messes of slobber. On the other hand, when a kelpie or border collie gets above threshold, they tend to go internal, crouch down, shake and stare. Heelers bite. That is just what they are. Good things to know before you choose a dog, and also to know when you are trying to figure out where your dog is. It is really difficult to control a dog that is already above his threshold, so work on keeping him below it, and as you do, his threshold will probably rise and you can add a bit more pressure.